In just over a year, Microsoft went from having basically no real enterprise-class server virtualization technology to one that is at par and has VMware scared and running. Back in the middle of 2008, Microsoft’s server vritualization offering was Virtual Server 2005 that didn’t provide 64-bit guest support and really didn’t scale beyond having 3-4 guest sessions on a single server. Then Microsoft released Windows 2008 and Hyper-V with 64-bit guest session support and the ability to easily host 8, 10, 15 guest sessions on a single server. However for a year, VMware kept saying that Hyper-V didn’t provide “live migration,” the ability to move guest sessions during planned physical host downtime, and thus Hyper-V wasn’t "enterprise ready."
In true Microsoft competitive fashion, Microsoft not only released Live Migration in Hyper-V R2 that came with Windows 2008 R2, but Microsoft is including it for “free” as part of the normal Windows 2008 R2 enterprise (or datacenter) license, a technology that VMware used to charge $20,000+ for. A couple years ago, pretty much 100% of our server virtualization consulting business was focused on VMware. Today, half of our server virtualization consulting business is now based on Hyper-V R2, and it’s not that our VMware business has decreased, more and more organizations are virtualizing, and they are virtualizing under Hyper-V because it does come free with Windows, its gotten great reviews, it works extremely well, and Windows administrators that know how to run Microsoft Windows applications and thus know how to run, setup, and manage Hyper-V guest sessions.
The big thing that is new to Hyper-V is the whole Live Migration technology, which leverages Failover Clustering that allows a Hyper-V R2 guest session to failover to another Hyper-V R2 host server so that a Hyper-V host server can effectively be evaculated of any guest sessions to be patched, updated, upgraded, or maintained without ANY interruption to the operation of the guest session.
Quick Migration and Live Migration
There are two forms of automated migration provided by Windows Server 2008 R2 Hyper-V: Quick Migration and Live Migration. These migration processes can be used to increase service availability for planned and unplanned downtime.
Although both technologies achieve the same thing—moving virtual servers between Hyper-V hosts—they use different methods and mechanisms to achieve it. Both require at least two Hyper-V host servers in a cluster, attached to the same shared storage system. Usually, the shared storage is an iSCSI or Fibre Channel storage area network (SAN).
Quick Migration
Quick Migration provides a way to quickly move a virtual machine from one host server to another with a small amount of downtime.
In a Quick Migration, the guest virtual machine is suspended on one host and resumed on another host. This operation happens in the time it takes to transfer the active memory of the virtual machine over the network from the first host to the second host. For a host with 8GB of RAM, this might take about two minutes using a 1GB iSCSI connection.
Quick Migration was the fastest migration available for Windows Server 2008 Hyper-V. Microsoft made considerable investments in Hyper-V migration technologies, trying to reduce the time required to migrate virtual machines between Hyper-V hosts. The result was Live Migration, which has the same hardware requirements as Quick Migration, but with a near instantaneous failover time.
Live Migration
Since the release of Hyper-V V1 with Windows Server 2008, the number-one most-requested feature by customers is the ability to migrate running virtual machines between hosts, with no downtime. VMware's VMotion has been able to do this for some time. Finally, with Windows Server 2008 R2, it can be done natively with Hyper-V for no extra cost. This makes it a compelling reason to move to Hyper-V.
Live Migration uses failover clustering. The quorum model used for your cluster will depend on the number of Hyper-V nodes in your cluster. In this example, we will use two Hyper-V nodes in a Node and Disk Majority Cluster configuration. There will be one shared storage LUN used as the cluster quorum disk and another used as the Cluster Shared Volume (CSV) disk.
NOTE
If there is only one shared storage LUN available to the nodes when the cluster is formed, Windows will allocate that LUN as the cluster quorum disk and it will not be available to be used as a CSV disk.
This following describes how to use Hyper-V Live Migration to move virtual machines between clustered Hyper-V hosts.
Configuring the Cluster Quorum Witness Disk
Live Migration requires a Windows Server 2008 R2 cluster configured to use shared storage. Typically, these are LUNs provisioned on an iSCSI or Fibre Channel SAN. One LUN will be used as the witness disk for quorum and another will be used as a Cluster Shared Volume (CSV) to store the virtual machine images.
The LUN for the shared witness quorum disk must be configured before the cluster is formed, so that cluster manager can configure the cluster properly. Connect this LUN via iSCSI or Fibre Channel to both nodes you will use for the cluster. The disk must be initialized and formatted with an NTFS file format prior to cluster use. When properly configured, both nodes share the same online Basic disk and can access the disk at the same time.
IMPORTANT
The Windows cluster service will always use the first shared disk as the cluster quorum disk. Provision this disk first on each node.
Now that the shared storage witness disk has been configured, we can move on to installing the Windows cluster.
Installing the Failover Clustering Feature
Before a failover clustering can be deployed, the necessary feature must be installed. To install the Failover Clustering feature, perform the following steps:
1. Log on to the Windows Server 2008 R2 cluster node with an account with administrator privileges.
2. Click the Server Manager icon in the Windows taskbar.
3. Select the Features node in the tree pane when Server Manager opens.
4. In the tasks pane, select the Add Features link.
5. In the Select Features window, select Failover Clustering, click Next, and click Install on the Confirm Installation Selections page to install the feature.
6. When the installation completes, click Close to complete the installation and return to Server Manager.
7. Close Server Manager and install the Failover Clustering feature on each of the remaining cluster nodes.
Running the Validate a Configuration Wizard
Failover Cluster Management is used to administer the Failover Clustering feature. It can be run from Server Manager or as a separate MMC console. After the feature is installed, run the Validate a Configuration Wizard from the tasks pane of the Failover Cluster Management console. All nodes should be up and running when the wizard is run. To run the Validate a Configuration Wizard, perform the following steps:
1. Log on to one of the Windows Server 2008 R2 cluster nodes with an account with administrator privileges over all nodes in the cluster.
2. Click Start, click All Programs, click Administrative Tools, and select Failover Cluster Management.
3. When the Failover Cluster Management console opens, click the Validate a Configuration link in the Actions pane.
4. When the Validate a Configuration Wizard opens, click Next on the Before You Begin page.
5. On the Select Servers or a Cluster page, enter the name of a cluster node, and click the Add button. Repeat this process until all nodes are added to the list and click Next to continue.
6. On the Testing Options page, read the details that explain the requirements for all tests to pass in order to be supported by Microsoft. Select the Run All Tests (Recommended) option button, and click Next to continue.
7. On the Confirmation page, review the list of servers that will be tested and the list of tests that will be performed, and click Next to begin testing the servers.
NOTE
For years, administrators have complained that the Validate a Configuration Wizard window is too small. In Windows Server 2008 R2, administrators can finally resize the window by dragging the lower-right corner. This is not obvious, but try it—it works!
8. When the tests complete, the Summary page displays the results, and if the tests pass, click Finish to complete the Validate a Configuration Wizard. If the tests failed, click the View Report button to review the details and determine which test failed and why the test failed.
Even if the Validate a Configuration Wizard does not pass every test, depending on the test, creating a cluster might still be possible. After the Validation a Configuration Wizard is completed successfully, the cluster can be created.
Creating a Node and Disk Majority Cluster
When the failover cluster is first created, all nodes in the cluster should be up and running. To create the failover cluster, perform the following steps:
1. Log on to one of the Windows Server 2008 R2 cluster nodes with an account with administrator privileges over all nodes in the cluster.
2. Click Start, click All Programs, click Administrative Tools, and select Failover Cluster Management.
3. When the Failover Cluster Management console opens, click the Create a Cluster link in the Actions pane.
4. When the Create Cluster Wizard opens, click Next on the Before You Begin page.
5. On the Select Servers page, enter the name of each cluster node, and click the Add button. When all the nodes are listed, click Next to continue.
6. On the Validation Warning page, select No. I Do Not Require..... The validation test can be run after the configuration is complete. Click Next to continue.
7. On the Access Point for Administering the Cluster page, type in the name of the cluster, complete the IPv4 address, and click Next. The name you choose for the cluster will become a cluster computer account in Active Directory.
8. On the Confirmation page, review the settings, and click Next to create the cluster.
9. On the Summary page, review the results of the cluster creation process, and click Finish to return to the Failover Cluster Management console. If there are any errors, you can click the View Report button to reveal the detailed cluster creation report.
10. Back in the Failover Cluster Management console, select the cluster name in the tree pane. In the tasks pane, review the configuration of the cluster.
11. In the tree pane, select and expand Nodes to list all the cluster nodes.
12. Select Storage and review the cluster storage in the tasks pane. The shared storage disk will be listed as the witness disk in quorum. This disk is used to maintain quorum.
13. Expand Networks in the tree pane to review the list of networks. Select each network and review the names of the adapters in each network.
14. Click Validate Configuration in the Actions pane to start an automated review of the cluster configuration. See the previous section, “Running the Validate a Configuration Wizard,” for more details. Keep in mind that Microsoft support for the cluster will require a successful execution of the validation process.
Adding Additional Shared Storage
At this point, we have a Node and Disk Majority cluster using a shared witness disk to maintain quorum. We can now add the shared storage that will be used as a Cluster Shared Volume.
Another LUN must be provisioned for the Cluster Shared Volume to hold the virtual machine images used in Live Migration. This LUN may be a new unpartitioned volume or one that already contains virtual machine images and data.
Connect this LUN via iSCSI or Fibre Channel to both nodes in the cluster. The disk must be initialized and formatted with an NTFS file format prior to cluster use in the cluster. When properly configured, the disk will show in Disk Management on both nodes.
Next, we add the new shared disk to the cluster.
1. On one of the cluster nodes, open Failover Cluster Management.
2. Expand the Cluster and select Storage.
3. Click Add a Disk in the Actions pane.
4. Select the disk to add and click OK. The disk will be added to available storage.
Configuring Cluster Shared Volumes
Cluster Shared Volumes (CSVs) are a new concept for Windows Server 2008 R2. They provide the new capabilities required for Hyper-V Live Migration to work, and is why only Windows Server 2008 R2 nodes can participate in the cluster.
With CSV, any node can host the virtual machine and any node can access the VHD on shared storage, so virtual machine and disk ownership can move freely across cluster nodes without impacting any other resources on that shared disk.
To enable and configure Cluster Shared Volumes, perform the following steps from the Failover Cluster Management console:
1. Select the cluster name in the Failover Cluster Management console.
2. Click Enable Cluster Shared Volumes in the Actions pane.
3. The Enable Cluster Shared Volumes information dialog box will be displayed. Read the important information explaining that CSVs are only supported for the Hyper-V role on Windows Server 2008 R2 servers. Click the check box that you have read the notice and click OK.